Differencial diagnosis
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Difference between B. anthracis & Anthracoid organisms in culture
B. anthracis
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Anthracoid organisms
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Non motile
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generally motile
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Capsulated
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non capsulated
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Grows in long chains
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Grows in short chains
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No turbidity in broth
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Turbidity in broth
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Inverted fir tree in gelatin
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Atypical or absent
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Methylene blue reduced weakly
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Reduced strongly
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Haemolysis weak
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Strong
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Liquefaction of gelatin is slow
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Rapid
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Lecithinase reaction is weak
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Rapid
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Ferments salicin slowly
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Rapid
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Produces toxin, neutralised by B.anthracis antitoxin
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not neutralized
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Pathogenic to g.pigs & mice
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non pathogenic
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Susceptible to gamma phage
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not susceptible
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Difference between B. anthracis & Anthracoid organisms in blood smear stained with Polychrome methylene blue stain
B. anthracis
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Anthracoid
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Dark pink or Purple coloured capsules
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No capsule
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Organism rod stained blue
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Organism rod stained blue
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Ends truncated
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Ends bulged and rounded
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Single, pair or short chain
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Usually long chain
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Absence of spores
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Spores may be present
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Last modified: Monday, 4 June 2012, 4:20 AM